EUVD-2026-56595
GHSA-m9fr-m5pc-g6ww
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Local attack vector and low-privilege requirement match the description of an authorized local user escalating privileges; full C/I/A impact reflects SYSTEM-level escalation.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
3DescriptionCVE.org
Improper access control in Windows Cross Device Service allows an authorized attacker to elevate privileges locally.
AnalysisAI
Local privilege escalation in the Windows Cross Device Service (CVE-2026-66804) allows a low-privileged authenticated user to gain SYSTEM or elevated permissions on the local machine. The flaw stems from CWE-284 (Improper Access Control), meaning the service fails to adequately enforce authorization boundaries between user privilege levels. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires an existing low-privilege authenticated session on the target Windows machine (CVSS PR:L, AV:L). … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS base score of 7.8 (High) is well-supported by the vector: local access, low complexity, low privileges, no user interaction, and full C/H/I/A impact. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Apply the Microsoft security update addressing CVE-2026-66804, available through Windows Update and detailed at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66804. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, inventory all Windows systems running Cross Device Service and document which systems are operationally dependent on it. …
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Same weakness CWE-284 – Improper Access Control
View allSame technique Authentication Bypass
View allVendor StatusVendor
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